Frequency offset correction in narrowband machine-to-machine

ABSTRACT

A method in a node is disclosed. The method comprises receiving a signal, and obtaining a first oversampled received signal by sampling the received signal according to a symbol rate. The method further comprises estimating a first frequency offset based on the first oversampled received signal, the first frequency offset estimated using an estimation range limited to one of a bandwidth of the received signal or the symbol rate of the received signal, and obtaining a second oversampled received signal by sampling the received signal according to N times the symbol rate, wherein N is greater than 1. The method further comprises estimating a true frequency offset based on the first frequency offset estimate and the second oversampled received signal.

PRIORITY

This application is a continuation of co-pending U.S. patent applicationSer. No. 15/004,275 filed Jan. 22, 2016 which claims the benefit of U.S.Provisional Application 62/108,351 filed on Jan. 27, 2015 the disclosureof which is hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates, in general, to wireless communicationsand, more particularly, to frequency offset correction in narrowbandmachine-to-machine communications.

BACKGROUND

Cellular communication systems are being developed and improved formachine type communication (MTC), communication characterized by lowerdemands on data rates than for example mobile broadband, but with higherrequirements on, for example, low cost device design, better coverage,and an ability to operate for years on batteries without charging orreplacing the batteries. In the 3GPP GERAN specification group, cellularcommunication systems are being improved and developed in thefeasibility study named “Cellular System Support for Ultra LowComplexity and Low Throughput Internet of Things.” GSM is being evolved,and new “clean slate” systems (systems not based on current cellularsystems) are being developed.

One “clean slate” solution, called narrowband machine-to-machine (NBM2M), is a narrowband system with a carrier bandwidth of 200 kHz thattargets improved coverage compared to GSM systems, long battery life,and low complexity communication design.

One intention with this solution is to deploy it in spectrum that iscurrently used for GSM, by reducing the bandwidth used by GSM anddeploying NB M2M in the spectrum that becomes available. Anotherintention is to reuse existing GSM sites for the deployment of NB M2M.

In cellular communication systems, devices use a cell search procedure(or synchronization procedure) to understand which cell(s) to connectto. Some of the functions of a cell search procedure include detecting asuitable cell to camp on, and for that cell, obtaining the symbol andframe timing and synchronizing to the carrier frequency. Whensynchronizing to the carrier frequency, the mobile station needs tocorrect any erroneous frequency offsets that are present, and performsymbol timing alignment with the frame structure from the base station.

When the device wakes up from deep sleep, for example from being in apower saving state, the frequency offset is to a large extent due todevice clock inaccuracy (often assumed to be up to 20 ppm). The clockinaccuracy appears mainly as a frequency offset of the received signal,a continuous rotation of the received samples. For a system operatingwith a carrier frequency of 900 MHz, the maximum frequency offset is 18kHz (corresponding to 20 ppm inaccuracy). This offset needs to beestimated and corrected for.

The cell search procedure for NB M2M is described in GP-140864, “NBM2M—Cell Search Mechanism,” and GP-140861, “NB M2M—Frame IndexIndication Design.” A physical channel named Physical BroadcastSynchronization Channel (PBSCH) is dedicated to carrying thesynchronization signals, along with the broadcast system information. Aseparate downlink physical channel per base station is reserved forPBSCH, while the data channels are multiplexed by frequency divisionmultiplexing (FDM). In addition, the PBSCH operates with a reuse factorof 1, implying that the PBSCH of neighboring cells are completelyoverlapped in the frequency domain. This has the advantage of areduction in search complexity, but also results in interference fromall the other cells using the PBSCH. As described in GP-140864, frametiming estimation and frequency offset correction is performed using twodifferent sequences:

-   -   (a) Primary Synchronization Sequence (PSS): The PSS is used to        determine the frame timing alignment, along with a coarse        estimation of the frequency offset.    -   (b) Secondary Synchronization Sequence (SSS): The SSS is used to        obtain a finer estimate of the frequency offset.

FIG. 1 illustrates a frame structure for PBSCH. More particularly, FIG.1 illustrates a number of frames 5 a, 5 b, 5 c, 5 d (corresponding tothe Oth Frame, 1st Frame, 2nd Frame, and 63rd Frame, respectively).Every frame, such as 2nd Frame 5 c, consists of 960 symbols. In theexample frame structure shown in FIG. 1, 2nd Frame 5 c includes PSS 10,SSS 15, and Frame Index Indication Sequence (FIIS)+Broadcast InformationBlock (BIB) 20. In 2nd Frame 5 c, 256 symbols are dedicated to PSS 10,257 symbols are dedicated for SSS 15, and 447 symbols are dedicated toFIIS+BIB 20 (of the 447 symbols, 127 symbols are dedicated for FIIS, andthe remaining 320 symbols are for carrying the broadcast information ina BIB.

After switching on, an MTC device first needs to search for a signal ina viable frequency band. Signal detection is performed on the basis ofcomparing the amplitude of the peak from a correlation based detectorwith a pre-determined threshold. This is achieved by correlating thereceived signal with a known sequence, or a set of known sequences.Timing offset estimation and frequency offset estimation can then beperformed as described in GP-140864.

A problem with this approach arises from the fact that the maximumfrequency offset can be +/−18 kHz, whereas the signal bandwidth is only12 kHz. Since the maximum frequency offset is larger than the signalbandwidth, using the existing approach for detecting the frequencyoffset described in GP-140864 leads to aliasing. With existing frequencyoffset detectors that have a sampling rate corresponding to the signalbandwidth of 12 kHz, or those that perform linear operations such ascorrelation of the transmitted signal with the received signal in timeor frequency domain, one can only detect frequency offsets in the range[−6,6] kHz, and any frequency offset outside this range will be aliasedand incorrectly detected as being in the range [−6,6] kHz.

SUMMARY

To address the foregoing problems, disclosed is a method in a node. Themethod comprises receiving a signal, and obtaining a first oversampledreceived signal by sampling the received signal according to a symbolrate. The method further comprises estimating a first frequency offsetbased on the first oversampled received signal, the first frequencyoffset estimated using an estimation range limited to one of a bandwidthof the received signal or the symbol rate of the received signal. Themethod further comprises obtaining a second oversampled received signalby sampling the received signal according to N times the symbol rate,wherein N is greater than 1, and estimating a true frequency offsetbased on the first frequency offset estimate and the second oversampledreceived signal.

In certain embodiments, the node may comprise one of a wireless deviceor a network node. The method may further comprise determining, based onthe estimated first frequency offset, a set of possible aliasedfrequency offsets corresponding to the estimated first frequency offset.The method may further comprise estimating a time offset beforeestimating the first frequency offset as part of a cell searchprocedure. The method may further comprise using the estimated truefrequency offset to correct the received signal to enable reception ofsubsequent information. In certain embodiments, the subsequentinformation may comprise one or more of: a cell identity; a framenumber; broadcast information; and a data transmission.

In certain embodiments, estimating the true frequency offset based onthe first frequency offset estimate and the second oversampled receivedsignal may comprise correcting the estimated first frequency offsetusing the second oversampled received signal to extend the estimationrange outside of the signal bandwidth of the received signal or thesymbol rate of the received signal. In certain embodiments, estimatingthe true frequency offset based on the first frequency offset estimateand the second oversampled received signal may comprise: generating aplurality of signals, each of the plurality of generated signalscomprising a noise-free received signal with a frequency offset applied,the applied frequency offset comprising one of the determined set ofpossible aliased frequency offsets corresponding to the estimated firstfrequency offset; comparing one or more of the generated signals to thesecond oversampled received signal; and determining one of the appliedfrequency offsets to be the true frequency offset based at least in parton the comparison of one or more of the generated signals to the secondoversampled received signal. In certain embodiments, estimating the truefrequency offset based on the first frequency offset estimate and thesecond oversampled received signal may comprise: generating a noise-freereceived signal without a frequency offset applied; applying anelement-wise multiplication of the second oversampled received signalwith a complex conjugate of the generated noise-free received signal togenerate a new signal; and determining an aliased frequency offsetwithin the determined set of possible aliased frequency offsets to bethe true frequency offset, wherein the aliased frequency offsetdetermined to be the true frequency offset is an aliased frequencyoffset within the determined set of possible aliased frequency offsetsthat is most similar to the generated new signal.

Also disclosed is a node. The node comprises one or more processors. Theone or more processors are configured to receive a signal and obtain afirst oversampled received signal by sampling the received signalaccording to a symbol rate. The one or more processors are furtherconfigured to estimate a first frequency offset based on the firstoversampled received signal, the first frequency offset estimated usingan estimation range limited to one of a bandwidth of the received signalor the symbol rate of the received signal. The one or more processorsare further configured to obtain a second oversampled received signal bysampling the received signal according to N times the symbol rate,wherein N is greater than 1, and estimate a true frequency offset basedon the first frequency offset estimate and the second oversampledreceived signal.

Also disclosed is a computer program product. The computer programproduct comprises instructions stored on non-transient computer-readablemedia which, when executed by one or more processors, perform the actsof receiving a signal and obtaining a first oversampled received signalby sampling the received signal according to a symbol rate.

The instructions, when executed by the one or more processors, performthe acts of estimating a first frequency offset based on the firstoversampled received signal, the first frequency offset estimated usingan estimation range limited to one of a bandwidth of the received signalor the symbol rate of the received signal, and obtaining a secondoversampled received signal by sampling the received signal according toN times the symbol rate, wherein N is greater than 1. The instructions,when executed by the one or more processors, perform the act ofestimating a true frequency offset based on the first frequency offsetestimate and the second oversampled received signal.

Certain embodiments of the present disclosure may provide one or moretechnical advantages. As one example, certain embodiments may providefor correction of frequency offsets larger than the signal bandwidth. Incertain embodiments, this is achieved by making use of an oversampledreceived signal to correct the aliasing and allow for detection of thetrue frequency offset. This may advantageously allow the range offrequency offset detection to be extended from a limited offset range tothe full required offset detection range. As another example, certainembodiments may be applicable to any use case where the true frequencyoffset is larger than the signal bandwidth. Other advantages may bereadily apparent to one having skill in the art. Certain embodiments mayhave none, some, or all of the recited advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the disclosed embodiments and theirfeatures and advantages, reference is now made to the followingdescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 illustrates a frame structure for PBSCH.

FIG. 2 is a schematic diagram of a wireless communications network, inaccordance with certain embodiments;

FIG. 3 illustrates a method in a receiver for correction of aliasedfrequency offsets, in accordance with certain embodiments;

FIG. 4 illustrates an alternative method in a receiver for correction ofaliased frequency offsets, in accordance with certain embodiments;

FIG. 5 is a flow diagram of a method in a node, in accordance withcertain embodiments;

FIG. 6 is a schematic diagram of an exemplary wireless device, inaccordance with certain embodiments;

FIG. 7 is a schematic diagram of an exemplary network node, inaccordance with certain embodiments:

FIG. 8 is a schematic diagram of an exemplary radio network controlleror core network node, in accordance with certain embodiments;

FIG. 9 is a schematic diagram of an exemplary wireless device, inaccordance with certain embodiments:

FIG. 10 is a schematic diagram of an exemplary network node, inaccordance with certain embodiments; and

FIG. 11 is a block diagram illustrating an embodiment of a wirelesscommunication network, in accordance with certain embodiments.

DETAILED DESCRIPTION

As noted above, a problem with previous approaches arises from the factthat the maximum frequency offset can be larger than the signalbandwidth. In such a case, using existing approaches for detecting thefrequency offset leads to aliasing. For example, in some cases thefrequency offset can be +/−18 kHz, whereas the signal bandwidth is only12 kHz. With existing frequency offset detectors that have a samplingrate corresponding to the signal bandwidth of 12 kHz, or those thatperform linear operations such as correlation of the transmitted signalwith the received signal in time or frequency domain, one can onlydetect frequency offsets in the range [−6,6] kHz, and any frequencyoffset outside this range will be aliased and incorrectly detected asbeing in the range [−6,6] kHz.

The present disclosure contemplates various embodiments that may addressthese and other deficiencies of existing approaches. In some cases, thisis accomplished using a new method to correct the aliasing and detectthe true frequency offset. In one example embodiment, a node (such as,for example, a wireless device or a network node) receives a signal. Thenode obtains a first oversampled received signal by sampling thereceived signal according to a symbol rate. The node estimates a firstfrequency offset based on the first oversampled received signal, thefirst frequency offset estimated using an estimation range limited toone or a bandwidth of the received signal or the symbol rate of thereceived signal. The first frequency offset estimate lies in a limitedoffset range. This estimate is corrected for the ambiguity that is dueto aliasing.

In some cases, it may be possible to correct the aliasing and detect thetrue frequency offset by using correlation between the oversampled knowntransmitted sequence and the oversampled received sequence. Particularembodiments may use the correlation between the oversampled knowntransmitted sequence and the oversampled received sequence to get thetrue frequency offset. This may advantageously allow for the range offrequency offset detection to be extended from the first limited offsetrange, to the full required offset detection range, for example from[−6,6] kHz to [−18,18] kHz. Thus, frequency offsets larger than thesignal bandwidth are able to be corrected by making use of theoversampled received signal, and may be applicable to any use case wherethe true frequency offset is larger than the signal bandwidth.

FIG. 1 is a block diagram illustrating an embodiment of a network 100,in accordance with certain embodiments. Network 100 includes one or moreUE(s) 110 (which may be interchangeably referred to as wireless devices110, MTC UE 110, or MTC device 110), network node(s) 115 (which may beinterchangeably referred to as eNodeBs (eNBs) 115). UEs 110 maycommunicate with network nodes 115 over a wireless interface. Forexample, UE 110A may transmit wireless signals to one or more of networknodes 115, and/or receive wireless signals from one or more of networknodes 115. The wireless signals may contain voice traffic, data traffic,control signals, and/or any other suitable information. In someembodiments, an area of wireless signal coverage associated with anetwork node 115 may be referred to as a cell. In some embodiments, UEs110 may have device-to-device (D2D) capability. Thus, UEs 110 may beable to receive signals from and/or transmit signals directly to anotherUE. For example, UE 110A may be able to receive signals from and/ortransmit signals to UE 110B.

In certain embodiments, network nodes 115 may interface with a radionetwork controller. The radio network controller may control networknodes 115 and may provide certain radio resource management functions,mobility management functions, and/or other suitable functions. Incertain embodiments, the functions of the radio network controller maybe included in network node 115. The radio network controller mayinterface with a core network node. In certain embodiments, the radionetwork controller may interface with the core network node via aninterconnecting network. The interconnecting network may refer to anyinterconnecting system capable of transmitting audio, video, signals,data, messages, or any combination of the preceding. The interconnectingnetwork may include all or a portion of a public switched telephonenetwork (PSTN), a public or private data network, a local area network(LAN), a metropolitan area network (MAN), a wide area network (WAN), alocal, regional, or global communication or computer network such as theInternet, a wireline or wireless network, an enterprise intranet, or anyother suitable communication link, including combinations thereof.

In some embodiments, the core network node may manage the establishmentof communication sessions and various other functionalities for UEs 110.UEs 110 may exchange certain signals with the core network node usingthe non-access stratum layer. In non-access stratum signaling, signalsbetween UEs 110 and the core network node may be transparently passedthrough the radio access network. In certain embodiments, network nodes115 may interface with one or more network nodes over an internodeinterface. For example, network nodes 115A and 115B may interface overan X2 interface.

As described above, example embodiments of network 100 may include oneor more wireless devices 110, and one or more different types of networknodes capable of communicating (directly or indirectly) with wirelessdevices 110.

In some embodiments, the non-limiting term UE is used. UEs 110 describedherein can be any type of wireless device capable of communicating withnetwork nodes 115 or another UE over radio signals. UE 110 may also be aradio communication device, target device, D2D UE,machine-type-communication UE or UE capable of machine-to-machinecommunication (M2M), low-cost and/or low-complexity UE, a sensorequipped with UE, Tablet, mobile terminals, smart phone, laptop embeddedequipped (LEE), laptop mounted equipment (LME), USB dongles. CustomerPremises Equipment (CPE), etc. UE 110 may operate under either normalcoverage or enhanced coverage with respect to its serving cell. Theenhanced coverage may be interchangeably referred to as extendedcoverage. UE 110 may also operate in a plurality of coverage levels(e.g., normal coverage, enhanced coverage level 1, enhanced coveragelevel 2, enhanced coverage level 3 and so on).

Also, in some embodiments generic terminology, “radio network node” (orsimply “network node”) is used. It can be any kind of network node,which may comprise a base station (BS), radio base station, Node B, basestation (BS), multi-standard radio (MSR) radio node such as MSR BS,evolved Node B (eNB), network controller, radio network controller(RNC), base station controller (BSC), relay node, relay donor nodecontrolling relay, base transceiver station (BTS), access point (AP),radio access point, transmission points, transmission nodes. RemoteRadio Unit (RRU), Remote Radio Head (RRH), nodes in distributed antennasystem (DAS), Multi-cell/multicast Coordination Entity (MCE), corenetwork node (e.g., MSC, MME etc). O&M, OSS, SON, positioning node(e.g., E-SMLC), MDT, or any suitable network node.

The terminology such as network node and UE should be considerednon-limiting and does in particular not imply a certain hierarchicalrelation between the two: in general “eNodeB” could be considered asdevice 1 and “UE” device 2, and these two devices communicate with eachother over some radio channel. The term “node” used herein may be usedto denote a UE or a network node.

Example embodiments of UE 110, network nodes 115, and other networknodes (such as radio network controller or core network node) aredescribed in more detail below with respect to FIGS. 6-11.

Although FIG. 1 illustrates a particular arrangement of network 100X),the present disclosure contemplates that the various embodimentsdescribed herein may be applied to a variety of networks having anysuitable configuration. For example, network 100 may include anysuitable number of UEs 110 and network nodes 115, as well as anyadditional elements suitable to support communication between UEs orbetween a UE and another communication device (such as a landlinetelephone). Furthermore, although certain embodiments may be describedas implemented in a Long Term Evolution (LTE) network, the embodimentsmay be implemented in any appropriate type of telecommunication systemsupporting any suitable communication standards and using any suitablecomponents, and are applicable to any radio access technology (RAT) ormulti-RAT systems in which the UE receives and/or transmits signals(e.g., data). For example, the various embodiments described herein maybe applicable to LTE, LTE-Advanced. UMTS, HSPA, GSM, cdma2000, WiMax,WiFi, another suitable radio access technology, or any suitablecombination of one or more radio access technologies. Although certainembodiments may be described in the context of wireless transmissions inthe downlink, the present disclosure contemplates that the variousembodiments are equally applicable in the uplink.

In certain embodiments, depending on the scenario, a node, such aswireless device 110, first estimates the frequency offset with anestimation range that is limited to the bandwidth of the signal or thesymbol rate of the signal. Then, wireless device 110 applies thetechnique described herein to extend the range outside of the signalbandwidth, up to the maximum frequency offset range that the receiverneeds to handle.

As an example, consider the procedure proposed to be used in NB M2Mdescribed in GP-140864. Note, however, that this is only one example,and the present disclosure contemplates that the various embodimentsdescribed herein can be applied to other systems where the same problemarises. Similarly, although the following example focuses on wirelessdevice 110, the various embodiments described herein are applicable toany suitable node, such as network node 115, as well as any othersuitable device having a receiver and susceptible to potential frequencyoffsets that are larger than the signal bandwidth.

In certain embodiments, a node, such as wireless device 110 (which maybe an MTC device), receives a signal. Wireless device 110 first obtainsthe frame timing using the PSS (such as PSS 10 described above).Wireless device 110 then uses the SSS (such as SSS 15 described above)for determining the frequency offset. Wireless device 110 may thenobtain a first oversampled received signal by sampling the receivedsignal according to a symbol rate. In some embodiments, the receivedsignal may be sampled according to the symbol rate (i.e., oversamplingfactor 1) to obtain the first oversampled received signal.

When wireless device 110 wakes up from deep sleep, the inaccuracies inthe device clocks can give rise to an initial frequency offset. In theNB M2M example, the initial frequency offset may be up to +/−18 kHz(corresponding to 20 ppm for a carrier frequency of 900 MHz). A firstfrequency offset estimation based on the first oversampled receivedsignal, for example as described in GP-140864, is determined as apotential frequency offset. However, since the signal bandwidth is only12 kHz, the frequency offset detection is limited to the range +/−6 kHz.Frequency offsets outside +/−6 kHz are aliased and appear as offsetswithin the range +/−6 kHz. For example, a frequency offset of 15 kHzappears as an offset of 3 kHz. In order to resolve this detection rangeproblem, certain embodiments use the correlation between the oversampledreceived signal and the known oversampled transmitted signal to correctsuch ambiguities. This may be applied to all scenarios where the actualfrequency offset to be detected is larger than the signal bandwidth orsymbol rate, and is not limited to offset methods disclosed inGP-140864.

As described above, when the actual frequency offset is larger than thesymbol bandwidth, previous approaches provide an aliased value of thetrue frequency offset. Wireless device 110 corrects this ambiguity byestimating a true frequency offset based on the first frequency offsetestimate and a second oversampled received signal. In certainembodiments, the second oversampled received signal is obtained bysampling the received signal according to N times the symbol rate, whereN is greater than 1 (i.e., oversampling factor N).

In some embodiments, estimating a true frequency offset based on thefirst frequency offset estimate and the second oversampled receivedsignal may comprise generating decision metrics, each associated with afrequency offset in a set of possible aliased frequency offsets, whichis determined by the first frequency offset estimate. For example,wireless device 110 may determine, based on the estimated firstfrequency offset, a set of possible aliased frequency offsetscorresponding to the estimated first frequency offset.

In certain embodiments, to estimate a true frequency offset based on thefirst frequency offset estimate and a second oversampled received signalwireless device 110 may correct the first frequency offset estimate byusing the second oversampled received signal. As described above, thefirst frequency offset estimate lies in a (too) limited frequency offsetrange. The true frequency offset may be estimated in any suitablemanner. As one example, wireless device 110 may generate a plurality ofsignals, each of the plurality of signals corresponding to a noise-freereceived signal with a certain frequency offset applied. In some cases,each potential frequency offset may be the first frequency offsetestimate, adjusted with an additional offset corresponding to thealiasing that may have happened when forming the first frequency offsetestimate. Then, each generated signal is compared with the secondoversampled received signal to determine which potential frequencyoffset gives the best match.

As another example, wireless device 110 may generate a noise-freereceived signal without a frequency offset applied. Wireless device 110may then apply an element-wise multiplication of the second oversampledreceived signal with a complex conjugate of the generated noise-freereceived signal to generate a new signal. The resulting new signal maybe investigated to determine an aliased frequency offset within thedetermined set of possible aliased frequency offsets that is the truefrequency offset. In some cases, the aliased frequency offset determinedto be the true frequency offset is an aliased frequency offset withinthe determined set of possible aliased frequency offsets that is mostsimilar to the generated new signal.

In particular embodiments, wireless device 110 may also perform thedot-product of the resulting new signal with a number of frequencyoffset phasors, where each phasor corresponds to a potential frequencyoffset. Each potential frequency offset is the first frequency offsetestimate, adjusted with an additional offset corresponding to thealiasing that may have happened when forming the first estimate. Theneach generated signal is compared with the received signal, to determinewhich potential frequency offset gives the best match.

The present disclosure contemplates that any of the embodimentsdescribed herein may be used in a cell search procedure where a timeoffset estimation has been performed before the frequency offsetestimation is performed. Similarly, any of the embodiments describedherein may be used in a cell search procedure, where the resultingfrequency offset estimate is used to correct the received signal forreception of subsequent information. For example, the subsequentinformation may include the reception of the frame number, the receptionof the cell identity, the reception of the cell identity, followed bythe reception of the frame number, the reception of broadcastinformation, the reception of data transmission, etc.

FIG. 3 illustrates a method 300 in a receiver for correction of aliasedfrequency offsets, in accordance with certain embodiments. The receivermay be included in a wireless device or network node, such as wirelessdevice 110 or network node 116 described above, or in any other suitabledevice. At block 305, SSS 15 is up-sampled. At block 310, up-sampled SSS15 is passed through a filter corresponding to the transmit filter inthe transmitter and the receive filter in the receiver. Although FIG. 3illustrates an example in which the filter corresponding to the transmitfilter in the transmitter and the receive filter in the receivertogether can be seen as a raised cosine filter, the present disclosurecontemplates that any suitable filter may be used. As a result, NewSequence A is obtained at block 315. New sequence A at block 315corresponds to what would be the oversampled received SSS in absence ofnoise in a frequency-flat non-fading channel.

As noted above, when an MTC device 110 wakes up from deep sleep, theinaccuracies in the device clocks can give rise to an initial frequencyoffset (up to +/−18 kHz in NB M2M, for example). A first frequencyoffset estimation, such as one determined in accordance with GP-140864,is determined as a potential frequency offset. The estimated frequencyoffset obtained from the first basic frequency offset estimation, suchas the one in GP-140864, can be denoted as f. A set of possible aliasedfrequency offsets 320 corresponding to f is formed as follows:

F={f,f−12,f+12,f−24,f+24} kHz.  (1)

A smaller or larger set can also be envisioned, with equal and non-equalspacing of the offsets.

Since the maximum frequency offset in this example is +/−18 kHz, anyvalue in the set F outside the range [−18,18] kHz is discarded at block325. At block 330, the remaining values from the set are input to afrequency offset phasor, which is a vector of the same length as SS 15and is of the form:

$\begin{matrix}{\lbrack {1,e^{j\; \frac{2\pi \; f}{S\mspace{11mu} B}},e^{j\; \frac{4\pi \; f}{S\mspace{11mu} B}},\ldots \mspace{14mu},e^{j\; \frac{2{({{NS} - 1})}\pi \; f}{\mspace{34mu} {S\mspace{50mu} B}}}} \rbrack,{f \in F}} & (2)\end{matrix}$

Here, N is the length of the (non-oversampled) SSS 15 in number ofsymbols. S is the oversampling factor (i.e., the number of samples persymbol). B is the bandwidth in kHz.

The thick arrows (arrow 335, 345, and 360) illustrated in FIG. 3indicate that multiple such vectors are formed, each corresponding to avalue in the set of possible aliased frequency offsets 320 (denoted as Fin Equation 1 above). At block 340, an element-wise multiplication isperformed on the up-sampled and interpolated SSS 15 with each of thefrequency offset phasors generated at block 330. The resulting signals345 are fed as input to block 350, which calculates the dot productbetween each of the signals 345 and oversampled received signal 355 (thepart corresponding to SSS 15, which is known after frame timing). Thenumber of values obtained 360 is equal to the number of elements in F(the set of possible aliased frequency offsets 320). At block 365, thefrequency offset corresponding to the maximum of these values isdetermined as the true frequency offset and final frequency offsetestimate. At block 370, the final frequency offset is output.

In certain embodiments, not the full length of the signal but only apart of the transmitted and received signal corresponding to thesequence (here. SSS 15) is used to determine the frequency offsetaccording to the above description. As one example, this part of thetransmitted and received signal may consist of all samples of thesignal, but over a length that is shorter than the full frequency offsetestimation signal. As another example, the part of the transmitted andreceived signal can be all oversampled samples except the onescorresponding to the non-oversampled symbol positions, since thesepositions would give the same contribution to the dot productindependent of the potential offset f in the set of possible aliasedfrequency offsets 320 (F).

FIG. 4 illustrates an alternative method in a receiver for correction ofaliased frequency offsets, in accordance with certain embodiments. Inthe example illustrated in FIG. 4, the complex conjugate of thetransmitted signal used for frequency offset estimation (here, SSS 15 a)is up-sampled at block 405 to correspond to the sampling rate of theoversampled received signal 410. At block 415, the up-sampled complexconjugate of the transmitted signal used for frequency offset estimationis filtered with a filter corresponding to the transmit and receivefilters (e.g., a raised cosine filter). This way, New Sequence B(corresponding to the complex conjugate of the oversampled transmittedsignal) is generated at block 420. At block 425, New Sequence Bgenerated at block 420 is element-wise multiplied with oversampledreceived signal corresponding to SSS 410. This results in New Sequence Cat block 430. At block 435, New Sequence C generated at block 430 isinvestigated to find the frequency offset that has the best match. Inthis investigation, the extra samples available in the oversampled NewSequence C are used to determine the correct frequency offset in a widerrange of potential offsets.

In the example illustrated in FIG. 4, the investigation at block 435utilizes the results of the application of a first frequency offsetestimation, for example the one described in GP-140864, to find apotential frequency offset. The estimated frequency offset obtained fromthe first basic frequency offset estimation, such as the one inGP-140864, can be denoted as f. A set of possible aliased frequencyoffsets 440 corresponding to f is formed as follows:

F={f,f−12,f+12,f−24,f+24} kHz.  (3)

A smaller or larger set can also be envisioned, with equal and non-equalspacing of the offsets.

Using the existing NB M2M approach as an example, the maximum frequencyoffset is +/−18 kHz. Thus, any value in the set F outside the range[−18,18] kHz is discarded at block 445. At block 450, the remainingvalues from the set are input to a frequency offset phasor. Arrow 455indicates that multiple such vectors are formed, each corresponding to avalue in the set of possible aliased frequency offsets 440 (denoted as Fin Equation 3 above).

To find the frequency offset that gives the best match at block 435, onepossibility is to calculate the dot-product of the New Sequence C 430and each possible phasor 455 generated at block 450 (corresponding toeach possible f in the set F). An alternative is to create asub-sequence of length S samples from New Sequence C 430. Thesub-sequence can be one part of New Sequence C 430, or it can be acombination of multiple parts of New Sequence C 430. In someembodiments, New Sequence C 430 is split into a number of successivesub-sequences of S samples. Then, the sub-sequences may each bemultiplied with a complex number. The complex number may be the complexconjugate of a unit amplitude complex number with the same phase as thefirst sample in each sub-sequence. Then, one or more sub-sequences areadded together. The result of the sum of sub-sequences is a sub-sequenceof S samples. The samples of this sub-sequence are then investigated atblock 435 to determine the frequency offset that provides the bestmatch. One way is to compare the resulting sub-sequence to a set ofS-length phasors, corresponding to the set of candidate frequencyoffsets:

$\begin{matrix}\lbrack {1,e^{j\; \frac{2\pi \; f}{S\mspace{11mu} B}},e^{j\; \frac{4\pi \; f}{S\mspace{11mu} B}},\ldots \mspace{14mu},e^{j\; \frac{2{({S - 1})}\pi \; f}{\mspace{34mu} {S\mspace{40mu} B}}}} \rbrack & (5)\end{matrix}$

In some embodiments, the first sample is excluded from the comparisonsince it is already adjusted to have value 1. In some embodiments, asmall subset of the S samples, or only 1 sample, of the sub-sequence isused to determine which of the potential frequency offsets has the bestmatch. This can be done by comparing the samples to the correspondingvalues of a phasor configured for the frequency offset f.

With either alternative, the frequency offset having the best matchfound as a result of the investigation at block 435 is determined as thetrue frequency offset and final frequency offset estimate. At block 460,the final frequency offset is output.

FIG. 5 is a flow diagram of a method 500 in a node, in accordance withcertain embodiments. The method begins at step 504, where the nodereceives a signal. In certain embodiments, the node may be one of awireless device or a network node.

At step 508, the node obtains a first oversampled received signal bysampling the received signal according to a symbol rate. At step 512,the node estimates a first frequency offset based on the firstoversampled received signal, the first frequency offset estimated usingan estimation range limited to one of a bandwidth of the received signalor the symbol rate of the received signal.

At step 516, the node obtains a second oversampled received signal bysampling the received signal according to N times the symbol rate,wherein N is greater than 1.

At step 520, the node estimates a true frequency offset based on thefirst frequency offset estimate and the second oversampled receivedsignal. In certain embodiments, estimating the true frequency offsetbased on the first frequency offset estimate and the second oversampledreceived signal may comprise correcting the estimated first frequencyoffset using the second oversampled received signal to extend theestimation range outside of the signal bandwidth of the received signalor the symbol rate of the received signal.

In certain embodiments, the method may further comprise determining,based on the estimated first frequency offset, a set of possible aliasedfrequency offsets corresponding to the estimated first frequency offset.The method may further comprise estimating a time offset beforeestimating the first frequency offset as part of a cell searchprocedure. The method may further comprise using the estimated truefrequency offset to correct the received signal to enable reception ofsubsequent information. In certain embodiments, the subsequentinformation may comprise one or more of: a cell identity; a framenumber; broadcast information; and data transmission.

The true frequency offset estimated based on the first frequency offsetestimate and the second oversampled received signal may be estimated inany suitable manner. As one example, estimating the true frequencyoffset based on the first frequency offset estimate and the secondoversampled received signal may comprise: generating a plurality ofsignals, each of the plurality of generated signals comprising anoise-free received signal with a frequency offset applied, the appliedfrequency offset comprising one of the determined set of possiblealiased frequency offsets corresponding to the estimated first frequencyoffset: comparing one or more of the generated signals to the secondoversampled received signal: and determining one of the appliedfrequency offsets to be the true frequency offset based at least in parton the comparison of one or more of the generated signals to the secondoversampled received signal.

As another example, estimating the true frequency offset based on thefirst frequency offset estimate and the second oversampled receivedsignal may comprise: generating a noise-free received signal without afrequency offset applied; applying an element-wise multiplication of thesecond oversampled received signal with a complex conjugate of thegenerated noise-free received signal to generate a new signal: anddetermining an aliased frequency offset within the determined set ofpossible aliased frequency offsets to be the true frequency offset,wherein the aliased frequency offset determined to be the true frequencyoffset is an aliased frequency offset within the determined set ofpossible aliased frequency offsets that is most similar to the generatednew signal.

FIG. 6 is a block schematic of an exemplary wireless device 110, inaccordance with certain embodiments. Wireless device 110 may refer toany type of wireless device communicating with a node and/or withanother wireless device in a cellular or mobile communication system.Examples of wireless device 110 include a mobile phone, a smart phone, aPDA (Personal Digital Assistant), a portable computer (e.g., laptop,tablet), a sensor, a modem, a machine-type-communication (MTC)device/machine-to-machine (M2M) device, laptop embedded equipment (LEE),laptop mounted equipment (LME), USB dongles, a D2D capable device, oranother device that can provide wireless communication. A wirelessdevice 110 may also be referred to as UE, a station (STA), a device, ora terminal in some embodiments. Wireless device 110 includes transceiver610, processor 620, and memory 630. In some embodiments, transceiver 610facilitates transmitting wireless signals to and receiving wirelesssignals from network node 115 (e.g., via an antenna), processor 620executes instructions to provide some or all of the functionalitydescribed above as being provided by wireless device 110, and memory 630stores the instructions executed by processor 620.

Processor 620 may include any suitable combination of hardware andsoftware implemented in one or more modules to execute instructions andmanipulate data to perform some or all of the described functions ofwireless device 110, such as the functions of wireless device 110described above in relation to FIGS. 1-5. In some embodiments, processor620 may include, for example, one or more computers, one or more centralprocessing units (CPUs), one or more microprocessors, one or moreapplications, one or more application specific integrated circuits(ASICs), one or more field programmable gate arrays (FPGAs) and/or otherlogic.

Memory 630 is generally operable to store instructions, such as acomputer program, software, an application including one or more oflogic, rules, algorithms, code, tables, etc. and/or other instructionscapable of being executed by a processor. Examples of memory 630 includecomputer memory (for example. Random Access Memory (RAM) or Read OnlyMemory (ROM)), mass storage media (for example, a hard disk), removablestorage media (for example, a Compact Disk (CD) or a Digital Video Disk(DVD)), and/or or any other volatile or non-volatile, non-transitorycomputer-readable and/or computer-executable memory devices that storeinformation, data, and/or instructions that may be used by processor620.

Other embodiments of wireless device 110 may include additionalcomponents beyond those shown in FIG. 6 that may be responsible forproviding certain aspects of the wireless device's functionality,including any of the functionality described above and/or any additionalfunctionality (including any functionality necessary to support thesolution described above). As just one example, wireless device 110 mayinclude input devices and circuits, output devices, and one or moresynchronization units or circuits, which may be part of the processor620. Input devices include mechanisms for entry of data into wirelessdevice 110. For example, input devices may include input mechanisms,such as a microphone, input elements, a display, etc. Output devices mayinclude mechanisms for outputting data in audio, video and/or hard copyformat. For example, output devices may include a speaker, a display,etc.

FIG. 7 is a block schematic of an exemplary network node 115, inaccordance with certain embodiments. Network node 115 may be any type ofradio network node or any network node that communicates with a UEand/or with another network node. Examples of network node 115 includean eNodeB, a node B, a base station, a wireless access point (e.g., aWi-Fi access point), a low power node, a base transceiver station (BTS),relay, donor node controlling relay, transmission points, transmissionnodes, remote RF unit (RRU), remote radio head (RRH), multi-standardradio (MSR) radio node such as MSR BS, nodes in distributed antennasystem (DAS), O&M, OSS, SON, positioning node (e.g., E-SMLC), MDT, orany other suitable network node. Network nodes 115 may be deployedthroughout network 100 as a homogenous deployment, heterogeneousdeployment, or mixed deployment. A homogeneous deployment may generallydescribe a deployment made up of the same (or similar) type of networknodes 115 and/or similar coverage and cell sizes and inter-sitedistances. A heterogeneous deployment may generally describe deploymentsusing a variety of types of network nodes 115 having different cellsizes, transmit powers, capacities, and inter-site distances. Forexample, a heterogeneous deployment may include a plurality of low-powernodes placed throughout a macro-cell layout. Mixed deployments mayinclude a mix of homogenous portions and heterogeneous portions.

Network node 115 may include one or more of transceiver 710, processor720, memory 730, and network interface 740. In some embodiments,transceiver 710 facilitates transmitting wireless signals to andreceiving wireless signals from wireless device 110 (e.g., via anantenna), processor 720 executes instructions to provide some or all ofthe functionality described above as being provided by a network node115, memory 730 stores the instructions executed by processor 720, andnetwork interface 740 communicates signals to backend networkcomponents, such as a gateway, switch, router, Internet, Public SwitchedTelephone Network (PSTN), core network nodes or radio networkcontrollers 130, etc.

Processor 720 may include any suitable combination of hardware andsoftware implemented in one or more modules to execute instructions andmanipulate data to perform some or all of the described functions ofnetwork node 115, such as those described above in relation to FIGS. 1-5above. In some embodiments, processor 720 may include, for example, oneor more computers, one or more central processing units (CPUs), one ormore microprocessors, one or more applications, and/or other logic.

Memory 730 is generally operable to store instructions, such as acomputer program, software, an application including one or more oflogic, rules, algorithms, code, tables, etc. and/or other instructionscapable of being executed by a processor. Examples of memory 730 includecomputer memory (for example, Random Access Memory (RAM) or Read OnlyMemory (ROM)), mass storage media (for example, a hard disk), removablestorage media (for example, a Compact Disk (CD) or a Digital Video Disk(DVD)), and/or or any other volatile or non-volatile, non-transitorycomputer-readable and/or computer-executable memory devices that storeinformation.

In some embodiments, network interface 740 is communicatively coupled toprocessor 720 and may refer to any suitable device operable to receiveinput for network node 115, send output from network node 115, performsuitable processing of the input or output or both, communicate to otherdevices, or any combination of the preceding. Network interface 740 mayinclude appropriate hardware (e.g., port, modem, network interface card,etc.) and software, including protocol conversion and data processingcapabilities, to communicate through a network.

Other embodiments of network node 115 may include additional componentsbeyond those shown in FIG. 7 that may be responsible for providingcertain aspects of the radio network node's functionality, including anyof the functionality described above and/or any additional functionality(including any functionality necessary to support the solutionsdescribed above). The various different types of network nodes mayinclude components having the same physical hardware but configured(e.g., via programming) to support different radio access technologies,or may represent partly or entirely different physical components.

FIG. 8 is a block schematic of an exemplary radio network controller orcore network node 130, in accordance with certain embodiments. Examplesof network nodes can include a mobile switching center (MSC), a servingGPRS support node (SGSN), a mobility management entity (MME), a radionetwork controller (RNC), a base station controller (BSC), and so on.The radio network controller or core network node 130 includes processor820, memory 830, and network interface 840. In some embodiments,processor 820 executes instructions to provide some or all of thefunctionality described above as being provided by the network node,memory 830 stores the instructions executed by processor 820, andnetwork interface 840 communicates signals to any suitable node, such asa gateway, switch, router, Internet, Public Switched Telephone Network(PSTN), network nodes 115, radio network controllers or core networknodes 130, etc.

Processor 820 may include any suitable combination of hardware andsoftware implemented in one or more modules to execute instructions andmanipulate data to perform some or all of the described functions of theradio network controller or core network node 130. In some embodiments,processor 820 may include, for example, one or more computers, one ormore central processing units (CPUs), one or more microprocessors, oneor more applications, and/or other logic.

Memory 830 is generally operable to store instructions, such as acomputer program, software, an application including one or more oflogic, rules, algorithms, code, tables, etc. and/or other instructionscapable of being executed by a processor. Examples of memory 830 includecomputer memory (for example, Random Access Memory (RAM) or Read OnlyMemory (ROM)), mass storage media (for example, a hard disk), removablestorage media (for example, a Compact Disk (CD) or a Digital Video Disk(DVD)), and/or or any other volatile or non-volatile, non-transitorycomputer-readable and/or computer-executable memory devices that storeinformation.

In some embodiments, network interface 840 is communicatively coupled toprocessor 820 and may refer to any suitable device operable to receiveinput for the network node, send output from the network node, performsuitable processing of the input or output or both, communicate to otherdevices, or any combination of the preceding. Network interface 840 mayinclude appropriate hardware (e.g., port, modem, network interface card,etc.) and software, including protocol conversion and data processingcapabilities, to communicate through a network.

Other embodiments of the network node may include additional componentsbeyond those shown in FIG. 8 that may be responsible for providingcertain aspects of the network node's functionality, including any ofthe functionality described above and/or any additional functionality(including any functionality necessary to support the solution describedabove).

FIG. 9 is a schematic block diagram of an exemplary wireless device, inaccordance with certain embodiments. Wireless device 110 may include oneor more modules. For example, wireless device 110 may include adetermining module 910, a communication module 920, a receiver module930, an input module 940, a display module 950, and any other suitablemodules.

Determining module 910 may perform the processing functions of wirelessdevice 110. For example, determining module 910 may obtain a firstoversampled received signal by sampling the received signal according toa symbol rate, and estimate a first frequency offset based on the firstoversampled received signal, the first frequency offset estimated usingan estimation range limited to one of a bandwidth of the received signalor the symbol rate of the received signal. As another example,determining module 910 may obtain a second oversampled received signalby sampling the received signal according to N times the symbol rate,wherein N is greater than 1. As yet another example, determining module910 may estimate a true frequency offset based on the first frequencyoffset estimate and the second oversampled received signal. Determiningmodule 910 may include or be included in one or more processors, such asprocessor 620 described above in relation to FIG. 6. Determining module910 may include analog and/or digital circuitry configured to performany of the functions of determining module 910 and/or processor 720described above. The functions of determining module 910 described abovemay, in certain embodiments, be performed in one or more distinctmodules.

Communication module 920 may perform the transmission functions ofwireless device 110. Communication module 920 may transmit messages toone or more of network nodes 115 of network 100. Communication module920 may include a transmitter and/or a transceiver, such as transceiver610 described above in relation to FIG. 6.

Communication module 920 may include circuitry configured to wirelesslytransmit messages and/or signals. In particular embodiments,communication module 920 may receive messages and/or signals fortransmission from determining module 910.

Receiving module 930 may perform the receiving functions of wirelessdevice 110. For example, receiving module 930 may receive a signal.Receiving module 930 may include a receiver and/or a transceiver.Receiving module 930 may include circuitry configured to wirelesslyreceive messages and/or signals. In particular embodiments, receivingmodule 930 may communicate received messages and/or signals todetermining module 910.

Input module 940 may receive user input intended for wireless device110. For example, the input module may receive key presses, buttonpresses, touches, swipes, audio signals, video signals, and/or any otherappropriate signals. The input module may include one or more keys,buttons, levers, switches, touchscreens, microphones, and/or cameras.The input module may communicate received signals to determining module910.

Display module 950 may present signals on a display of wireless device110. Display module 950 may include the display and/or any appropriatecircuitry and hardware configured to present signals on the display.Display module 950 may receive signals to present on the display fromdetermining module 910.

Determining module 910, communication module 920, receiving module 930,input module 940, and display module 950 may include any suitableconfiguration of hardware and/or software. Wireless device 110 mayinclude additional modules beyond those shown in FIG. 9 that may beresponsible for providing any suitable functionality, including any ofthe functionality described above and/or any additional functionality(including any functionality necessary to support the various solutionsdescribed herein).

FIG. 10 is a schematic block diagram of an exemplary network node 115,in accordance with certain embodiments. Network node 115 may include oneor more modules. For example, network node 115 may include determiningmodule 1010, communication module 1020, receiving module 1030, and anyother suitable modules. In some embodiments, one or more of determiningmodule 1010, communication module 1020, receiving module 1030, or anyother suitable module may be implemented using one or more processors,such as processor 720 described above in relation to FIG. 7. In certainembodiments, the functions of two or more of the various modules may becombined into a single module.

Determining module 1010 may perform the processing functions of networknode 115. As one example, determining module 1010 may obtain a firstoversampled received signal by sampling the received signal according toa symbol rate, and estimate a first frequency offset based on the firstoversampled received signal, the first frequency offset estimated usingan estimation range limited to one of a bandwidth of the received signalor the symbol rate of the received signal. As another example,determining module 1010 may obtain a second oversampled received signalby sampling the received signal according to N times the symbol rate,wherein N is greater than 1. As yet another example, determining module1010 may estimate a true frequency offset based on the first frequencyoffset estimate and the second oversampled received signal. Determiningmodule 1010 may include or be included in one or more processors, suchas processor 720 described above in relation to FIG. 7. Determiningmodule 1010 may include analog and/or digital circuitry configured toperform any of the functions of determining module 1010 and/or processor720 described above. The functions of determining module 1010 may, incertain embodiments, be performed in one or more distinct modules.

Communication module 1020 may perform the transmission functions ofnetwork node 115. Communication module 1020 may transmit messages to oneor more of wireless devices 110. Communication module 1020 may include atransmitter and/or a transceiver, such as transceiver 710 describedabove in relation to FIG. 7. Communication module 1020 may includecircuitry configured to wirelessly transmit messages and/or signals. Inparticular embodiments, communication module 1020 may receive messagesand/or signals for transmission from determining module 1010 or anyother module.

Receiving module 1030 may perform the receiving functions of networknode 115. As one example, receiving module 1030 may receive a signal.Receiving module 1030 may receive any suitable information from awireless device. Receiving module 1030 may include a receiver and/or atransceiver. Receiving module 1030 may include circuitry configured towirelessly receive messages and/or signals. In particular embodiments,receiving module 1030 may communicate received messages and/or signalsto determining module 1010 or any other suitable module.

Determining module 1010, communication module 1020, and receiving module1030 may include any suitable configuration of hardware and/or software.Network node 115 may include additional modules beyond those shown inFIG. 10 that may be responsible for providing any suitablefunctionality, including any of the functionality described above and/orany additional functionality (including any functionality necessary tosupport the various solutions described herein).

FIG. 11 is a block diagram illustrating an embodiment of a wirelesscommunication network, in accordance with certain embodiments. Moreparticularly, FIG. 11 illustrates a more detailed view of network node115 and wireless device 110. For simplicity, FIG. 11 depicts network1120, network nodes 115 and 115 a, and wireless device 110. Network node115 comprises processor 1102, storage 1103, interface 1101, and antenna1101 a. Similarly, wireless device 110 comprises processor 1112, storage1113, interface 1111 and antenna 1111 a. These components may worktogether in order to provide network node and/or wireless devicefunctionality, such as providing wireless connections in a wirelessnetwork and correcting frequency offset in NB M2M. For example, wirelessdevice 110 (including processor 1112, storage 1113, interface 1111, andantenna 1111 a) and network nodes 115 and/or 115 a (including processor1102, storage 1103, interface 1101, and antenna 1101 a) may perform someor all of the described functions of wireless device 110 and networknode 115 described above in relation to FIGS. 1-5. In differentembodiments, the wireless network may comprise any number of wired orwireless networks, network nodes, base stations, controllers, wirelessdevices, relay stations, and/or any other components that may facilitateor participate in the communication of data and/or signals whether viawired or wireless connections.

Network 1120 may comprise one or more IP networks, public switchedtelephone networks (PSTNs), packet data networks, optical networks, widearea networks (WANs), local area networks (LANs), wireless local areanetworks (WLANs), wired networks, wireless networks, metropolitan areanetworks, and other networks to enable communication between devices.

Network node 115 comprises processor 1102, storage 1103, interface 1101,and antenna 1101 a. These components are depicted as single boxeslocated within a single larger box. In practice however, network node115 may comprise multiple different physical components that make up asingle illustrated component (e.g., interface 1101 may compriseterminals for coupling wires for a wired connection and a radiotransceiver for a wireless connection). Similarly, network node 115 maybe composed of multiple physically separate components (e.g., a NodeBcomponent and a RNC component, a BTS component and a BSC component,etc.), which may each have their own respective processor, storage, andinterface components. In certain scenarios in which network node 115comprises multiple separate components (e.g., BTS and BSC components),one or more of the separate components may be shared among severalnetwork nodes. For example, a single RNC may control multiple NodeB's.In such a scenario, each unique NodeB and BSC pair, may be a separatenetwork node. In some embodiments, network node 115 may be configured tosupport multiple radio access technologies (RATs). In such embodiments,some components may be duplicated (e.g., separate storage 1103 for thedifferent RATs) and some components may be reused (e.g., the sameantenna 1101 a may be shared by the RATs).

Processor 1102 may be a combination of one or more of a microprocessor,controller, microcontroller, central processing unit, digital signalprocessor, application specific integrated circuit, field programmablegate array, or any other suitable computing device, resource, orcombination of hardware, software and/or encoded logic operable toprovide, either alone or in conjunction with other network node 115components, such as storage 1103, network node 115 functionality. Forexample, processor 1102 may execute instructions stored in storage 1103.Such functionality may include providing various wireless featuresdiscussed herein to a wireless devices, such as wireless device 110,including any of the features or benefits disclosed herein.

Storage 1103 may comprise any form of volatile or non-volatile computerreadable memory including, without limitation, persistent storage, solidstate memory, remotely mounted memory, magnetic media, optical media,random access memory (RAM), read-only memory (ROM), removable media, orany other suitable local or remote memory component. Storage 1103 maystore any suitable instructions, data or information, including softwareand encoded logic, utilized by network node 115. Storage 1103 may beused to store any calculations made by processor 1102 and/or any datareceived via interface 1101.

Network node 115 also comprises interface 1101 which may be used in thewired or wireless communication of signaling and/or data between networknode 115, network 1120, and/or wireless device 110. For example,interface 1101 may perform any formatting, coding, or translating thatmay be needed to allow network node 115 to send and receive data fromnetwork 1120 over a wired connection. Interface 1101 may also include aradio transmitter and/or receiver that may be coupled to or a part ofantenna 1101 a. The radio may receive digital data that is to be sentout to other network nodes or wireless devices via a wirelessconnection. The radio may convert the digital data into a radio signalhaving the appropriate channel and bandwidth parameters. The radiosignal may then be transmitted via antenna 1101 a to the appropriaterecipient (e.g., wireless device 110).

Antenna 1101 a may be any type of antenna capable of transmitting andreceiving data and/or signals wirelessly. In some embodiments, antenna1101 a may comprise one or more omni-directional, sector or panelantennas operable to transmit/receive radio signals between, forexample, 2 GHz and 66 GHz. An omni-directional antenna may be used totransmit/receive radio signals in any direction, a sector antenna may beused to transmit/receive radio signals from devices within a particulararea, and a panel antenna may be a line of sight antenna used totransmit/receive radio signals in a relatively straight line.

Wireless device 110 may be any type of wireless endpoint, mobilestation, mobile phone, wireless local loop phone, smartphone, userequipment, desktop computer, PDA, cell phone, tablet, laptop, VoIP phoneor handset, which is able to wirelessly send and receive data and/orsignals to and from a network node, such as network node 115 and/orother wireless devices. Wireless device 110 comprises processor 1112,storage 1113, interface 1111, and antenna 1111 a. Like network node 115,the components of wireless device 110 are depicted as single boxeslocated within a single larger box, however in practice a wirelessdevice may comprises multiple different physical components that make upa single illustrated component (e.g., storage 1113 may comprise multiplediscrete microchips, each microchip representing a portion of the totalstorage capacity).

Processor 1112 may be a combination of one or more of a microprocessor,controller, microcontroller, central processing unit, digital signalprocessor, application specific integrated circuit, field programmablegate array, or any other suitable computing device, resource, orcombination of hardware, software and/or encoded logic operable toprovide, either alone or in combination with other wireless device 110components, such as storage 1113, wireless device 110 functionality.Such functionality may include providing various wireless featuresdiscussed herein, including any of the features or benefits disclosedherein.

Storage 1113 may be any form of volatile or non-volatile memoryincluding, without limitation, persistent storage, solid state memory,remotely mounted memory, magnetic media, optical media, random accessmemory (RAM), read-only memory (ROM), removable media, or any othersuitable local or remote memory component. Storage 1113 may store anysuitable data, instructions, or information, including software andencoded logic, utilized by wireless device 110. Storage 1113 may be usedto store any calculations made by processor 1112 and/or any datareceived via interface 1111.

Interface 1111 may be used in the wireless communication of signalingand/or data between wireless device 110 and network node 115. Forexample, interface 1111 may perform any formatting, coding, ortranslating that may be needed to allow wireless device 110 to send andreceive data from network node 115 over a wireless connection. Interface1111 may also include a radio transmitter and/or receiver that may becoupled to or a part of antenna 1111 a. The radio may receive digitaldata that is to be sent out to network node 115 via a wirelessconnection. The radio may convert the digital data into a radio signalhaving the appropriate channel and bandwidth parameters. The radiosignal may then be transmitted via antenna 1111 a to network node 115.

Antenna 1111 a may be any type of antenna capable of transmitting andreceiving data and/or signals wirelessly. In some embodiments, antenna1111 a may comprise one or more omni-directional, sector or panelantennas operable to transmit/receive radio signals between 2 GHz and 66GHz. For simplicity, antenna 1111 a may be considered a part ofinterface 1111 to the extent that a wireless signal is being used.

In some embodiments, the components described above may be used toimplement one or more functional modules used in narrowbandmobile-to-mobile cell search. The functional modules may comprisesoftware, computer programs, sub-routines, libraries, source code, orany other form of executable instructions that are run by, for example,a processor. In general terms, each functional module may be implementedin hardware and/or in software. Preferably, one or more or allfunctional modules may be implemented by processors 1112 and/or 1102,possibly in cooperation with storage 1113 and/or 1103. Processors 1112and/or 1102 and storage 1113 and/or 1103 may thus be arranged to allowprocessors 1112 and/or 1102 to fetch instructions from storage 1113and/or 1103 and execute the fetched instructions to allow the respectivefunctional module to perform any features or functions disclosed herein.The modules may further be configured to perform other functions orsteps not explicitly described herein but which would be within theknowledge of a person skilled in the art.

Modifications, additions, or omissions may be made to the systems andapparatuses described herein without departing from the scope of thedisclosure. The components of the systems and apparatuses may beintegrated or separated. Moreover, the operations of the systems andapparatuses may be performed by more, fewer, or other components.

Additionally, operations of the systems and apparatuses may be performedusing any suitable logic comprising software, hardware, and/or otherlogic. As used in this document, “each” refers to each member of a setor each member of a subset of a set.

Modifications, additions, or omissions may be made to the methodsdescribed herein without departing from the scope of the disclosure. Themethods may include more, fewer, or other steps. Additionally, steps maybe performed in any suitable order.

Although this disclosure has been described in terms of certainembodiments, alterations and permutations of the embodiments will beapparent to those skilled in the art. Accordingly, the above descriptionof the embodiments does not constrain this disclosure. Other changes,substitutions, and alterations are possible without departing from thespirit and scope of this disclosure, as defined by the following claims.

Abbreviations used in the preceding description include:

3GPP Third Generation Partnership Project

BIB Broadcast Information Block

EDGE Enhanced Data Rates for GSM Evolution

FDM Frequency Division Multiplexing

FIIS Frame Index Indication Sequence

GERAN GSM EDGE Radio Access Network

GSM Global System for Mobile Communications

Hz Hertz

kHz kilo Hertz

MHz Mega Hertz

MTC Machine Type Communications

NB M2M Narrowband Machine to Machine

PBSCH Physical Broadcast Synchronization Channel

PSS Primary Synchronization Sequence

RC Raised Cosine

RRC Root Raised Cosine

SSS Secondary Synchronization Sequence

1-25. (canceled)
 26. A method in a node, comprising: receiving a signal;obtaining a first oversampled received signal by sampling the receivedsignal according to a symbol rate; estimating a first frequency offsetbased on the first oversampled received signal, the first frequencyoffset estimated using an estimation range limited to one of a bandwidthof the received signal or the symbol rate of the received signal;obtaining a second oversampled received signal by sampling the receivedsignal according to N times the symbol rate, wherein N is greater than1; correcting the first frequency offset by using the second oversampledreceived signal to extend the estimation range outside of the signalbandwidth of the received signal or the symbol rate of the receivedsignal; and estimating a true frequency offset based on the correctedfirst frequency offset and the second oversampled received signal. 27.The method of claim 26, wherein the node comprises one of a wirelessdevice or a network node.
 28. The method of claim 26, furthercomprising: determining a set of candidate aliased frequency offsetscorresponding to the corrected first frequency offset.
 29. The method ofclaim 28, wherein estimating the true frequency offset based on thecorrected first frequency offset and the second oversampled receivedsignal comprises: generating a plurality of signals, each of theplurality of generated signals comprising a noise-free received signalwith a frequency offset applied, the applied frequency offset comprisingone of the determined set of candidate aliased frequency offsetscorresponding to the estimated first frequency offset; comparing one ormore of the generated signals to the second oversampled received signal;and determining one of the applied frequency offsets to be the truefrequency offset based at least in part on the comparison of one or moreof the generated signals to the second oversampled received signal. 30.The method of claim 28, wherein estimating the true frequency offsetbased on the corrected first frequency offset and the second oversampledreceived signal comprises: generating a noise-free received signalwithout a frequency offset applied; applying an element-wisemultiplication of the second oversampled received signal with a complexconjugate of the generated noise-free received signal to generate a newsignal; and determining an aliased frequency offset within thedetermined set of candidate aliased frequency offsets to be the truefrequency offset, wherein the aliased frequency offset determined to bethe true frequency offset is an aliased frequency offset within thedetermined set of candidate aliased frequency offsets that is mostsimilar to the generated new signal.
 31. The method of claim 26, furthercomprising estimating a time offset before estimating the firstfrequency offset as part of a cell search procedure.
 32. The method ofclaim 26, further comprising using the determined true frequency offsetto correct the received signal to enable reception of subsequentinformation.
 33. The method of claim 32, wherein the subsequentinformation comprises one or more of: a cell identity; a frame number;broadcast information; and a data transmission.
 34. A node, comprising:a memory storing instructions; and a processor configured to execute theinstructions to: receive a signal; obtain a first oversampled receivedsignal by sampling the received signal according to a symbol rate;estimate a first frequency offset based on the first oversampledreceived signal, the first frequency offset estimated using anestimation range limited to one of a bandwidth of the received signal orthe symbol rate of the received signal; obtain a second oversampledreceived signal by sampling the received signal according to N times thesymbol rate, wherein N is greater than 1; correct the first frequencyoffset by using the second oversampled received signal to extend theestimation range outside of the signal bandwidth of the received signalor the symbol rate of the received signal; and estimate a true frequencyoffset based on the corrected first frequency offset and the secondoversampled received signal.
 35. The node of claim 34, wherein the nodecomprises one of a wireless device or a network node.
 36. The node ofclaim 34, wherein the processor is further configured to execute theinstructions to: determine a set of candidate aliased frequency offsetscorresponding to the corrected first frequency offset.
 37. The node ofclaim 36, wherein the processor is further configured to execute theinstructions to: generate a plurality of signals, each of the pluralityof generated signals comprising a noise-free received signal with afrequency offset applied, the applied frequency offset comprising one ofthe determined set of candidate aliased frequency offsets correspondingto the estimated first frequency offset; compare one or more of thegenerated signals to the second oversampled received signal; anddetermine one of the applied frequency offsets to be the true frequencyoffset based at least in part on the comparison of one or more of thegenerated signals to the second oversampled received signal.
 38. Thenode of claim 34, wherein the processor is further configured to executethe instructions to: generate a noise-free received signal without afrequency offset applied; apply an element-wise multiplication of thesecond oversampled received signal with a complex conjugate of thegenerated noise-free received signal to generate a new signal; anddetermine an aliased frequency offset within the determined set ofcandidate aliased frequency offsets to be the true frequency offset,wherein the aliased frequency offset determined to be the true frequencyoffset is an aliased frequency offset within the determined set ofcandidate aliased frequency offsets that is most similar to thegenerated new signal.
 39. The node of claim 34, wherein the processor isfurther configured to execute the instructions to: estimate a timeoffset before estimating the first frequency offset as part of a cellsearch procedure.
 40. The node of claim 34, wherein the processor isfurther configured to execute the instructions to: use the estimatedtrue frequency offset to correct the received signal to enable receptionof subsequent information.
 41. The node of claim 40, wherein thesubsequent information comprises one or more of: a cell identity; aframe number; broadcast information; and a data transmission.
 42. Anon-transitory computer-readable medium storing a program codeexecutable by a network device, wherein the execution of the programcode causes the network device to perform operations comprising:receiving a signal; obtaining a first oversampled received signal bysampling the received signal according to a symbol rate; estimating afirst frequency offset based on the first oversampled received signal,the first frequency offset estimated using an estimation range limitedto one of a bandwidth of the received signal or the symbol rate of thereceived signal; obtaining a second oversampled received signal bysampling the received signal according to N times the symbol rate,wherein N is greater than 1; correcting the first frequency offset byusing the second oversampled received signal to extend the estimationrange outside of the signal bandwidth of the received signal or thesymbol rate of the received signal; and estimating a true frequencyoffset based on the corrected first frequency offset and the secondoversampled received signal.
 43. The non-transitory computer-readablemedium of claim 42, further comprising: determining a set of candidatealiased frequency offsets corresponding to the corrected first frequencyoffset.
 44. The non-transitory computer-readable medium of claim 43,wherein estimating the true frequency offset based on the correctedfirst frequency offset and the second oversampled received signalcomprises: generating a plurality of signals, each of the plurality ofgenerated signals comprising a noise-free received signal with afrequency offset applied, the applied frequency offset comprising one ofthe determined set of candidate aliased frequency offsets correspondingto the estimated first frequency offset; comparing one or more of thegenerated signals to the second oversampled received signal; anddetermining one of the applied frequency offsets to be the truefrequency offset based at least in part on the comparison of one or moreof the generated signals to the second oversampled received signal. 45.The non-transitory computer-readable medium of claim 43, whereinestimating the true frequency offset based on the corrected firstfrequency offset and the second oversampled received signal comprises:generating a noise-free received signal without a frequency offsetapplied; applying an element-wise multiplication of the secondoversampled received signal with a complex conjugate of the generatednoise-free received signal to generate a new signal; and determining analiased frequency offset within the determined set of candidate aliasedfrequency offsets to be the true frequency offset, wherein the aliasedfrequency offset determined to be the true frequency offset is analiased frequency offset within the determined set of candidate aliasedfrequency offsets that is most similar to the generated new signal.